ObjectivesObjectives•Define basic components of electricityDefine basic components of electricity•Recognize the 3 electrical classifications of Recognize the 3 electrical classifications of materialsmaterials•Compare and contrast AC vs. DCCompare and contrast AC vs. DC•Explain the concept of groundingExplain the concept of grounding•Use Ohm’s law and Watt’s law to express the Use Ohm’s law and Watt’s law to express the relationship between current, voltage, and relationship between current, voltage, and resistanceresistance

Basic Electronics I

Electricity can be broken Electricity can be broken down into:down into:

Electric Charge Electric Charge VoltageVoltage CurrentCurrent ResistanceResistance

Negative & Positive ChargesNegative & Positive Charges What do the effects of electricity in TV, What do the effects of electricity in TV,

radio, a battery, and lightening all have in radio, a battery, and lightening all have in common? common?

Basic particles of electric charge with Basic particles of electric charge with opposite polarities.opposite polarities.

ElectronsElectrons The smallest amount of electrical charge The smallest amount of electrical charge

having the quality called negative polarity.having the quality called negative polarity. Electrons orbit the center of atoms.Electrons orbit the center of atoms.

ProtonsProtons The proton is a basic particle with positive The proton is a basic particle with positive

polarity.polarity. Protons are located in the nucleus of Protons are located in the nucleus of

atoms along with neutrons, particles which atoms along with neutrons, particles which have neutral polarity.have neutral polarity.

Electrically, all materials fall Electrically, all materials fall into 1 of 3 classifications:into 1 of 3 classifications:

ConductorsConductors Insulators Insulators Semi-ConductorsSemi-Conductors

Conductors Conductors Have 1 valence electronHave 1 valence electron Materials in which electrons can move Materials in which electrons can move

freely from atom to atom are called freely from atom to atom are called conductors. conductors.

In general all metals are good conductors. In general all metals are good conductors. The purpose of conductors is to allow The purpose of conductors is to allow

electrical current to flow with minimum electrical current to flow with minimum resistance.resistance.

InsulatorsInsulators Have 8 valence electronsHave 8 valence electrons Materials in which electrons tend to stay put and Materials in which electrons tend to stay put and

do not flow easily from atom to atom are termed do not flow easily from atom to atom are termed insulators. insulators.

Insulators are used to prevent the flow of Insulators are used to prevent the flow of electricity.electricity.

Insulating materials such as glass, rubber, or Insulating materials such as glass, rubber, or plastic are also called plastic are also called dielectricsdielectrics, meaning they , meaning they can store charges.can store charges.

Dielectric materials are used in components like Dielectric materials are used in components like capacitors which must store electric charges.capacitors which must store electric charges.

Semi-ConductorsSemi-Conductors Have 4 valence electronsHave 4 valence electrons Materials which are neither conductors nor Materials which are neither conductors nor

insulators insulators Common semi conductor materials are carbon, Common semi conductor materials are carbon,

germanium and silicone.germanium and silicone. Used in components like transistors Used in components like transistors

The Symbol for ChargeThe Symbol for Charge The symbol for charge is Q which stands The symbol for charge is Q which stands

for quantity.for quantity. The practical unit of charge is called the The practical unit of charge is called the

coulomb (C).coulomb (C). One coulomb is equal to the amount of One coulomb is equal to the amount of

charge of 6.25X10charge of 6.25X1018 18 electrons or protons electrons or protons stored in a dielectric.stored in a dielectric.

VoltageVoltage Potential refers to the the possibility of doing work.Potential refers to the the possibility of doing work. Any charge has the potential to do the work of Any charge has the potential to do the work of

attracting a similar charge or repulsing an attracting a similar charge or repulsing an opposite charge.opposite charge.

The symbol for potential difference is E (for The symbol for potential difference is E (for electromotive force)electromotive force)

The practical unit of potential difference is the volt The practical unit of potential difference is the volt (V)(V)

1 volt is a measure of the amount of work required 1 volt is a measure of the amount of work required to move 1C of chargeto move 1C of charge

CurrentCurrent When a charge is forced to move because When a charge is forced to move because

of a potential difference (voltage) current is of a potential difference (voltage) current is produced.produced.

In conductors - free electrons can be In conductors - free electrons can be forced to move with relative ease, since forced to move with relative ease, since they require little work to be moved.they require little work to be moved.

So current is charge in motion.So current is charge in motion. The more electrons in motion the greater The more electrons in motion the greater

the current.the current.

AmperesAmperes

Current indicates the intensity of the electricity in Current indicates the intensity of the electricity in motion. The symbol for current is I (for intensity) motion. The symbol for current is I (for intensity) and is measured in and is measured in amperes.amperes.

The definition of current is: I = Q/T The definition of current is: I = Q/T Where I is current in amperes, Q is charge in Where I is current in amperes, Q is charge in

coulombs, and T is time in seconds.coulombs, and T is time in seconds.

1 ampere = 1 coulomb per 1 ampere = 1 coulomb per secondsecond

ResistanceResistance Opposition to the flow of current is termed Opposition to the flow of current is termed

resistance.resistance. The fact that a wire can become hot from The fact that a wire can become hot from

the flow of current is evidence of the flow of current is evidence of resistance.resistance.

Conductors have very little resistance.Conductors have very little resistance. Insulators have large amounts of Insulators have large amounts of

resistance.resistance.

OhmsOhms The practical unit of resistance is the The practical unit of resistance is the

ohm ohm designated by the Greek letter designated by the Greek letter omegaomega:: Ω Ω

A resistor is an electronic component A resistor is an electronic component designed specifically to provide designed specifically to provide resistance.resistance.

Closed CircuitsClosed Circuits In applications requiring the use of current, In applications requiring the use of current,

electrical components are arranged in the electrical components are arranged in the form of a circuit.form of a circuit.

A circuit is defined as a path for current A circuit is defined as a path for current flow.flow.

Common Electronic Common Electronic Component SymbolsComponent Symbols

A Complex Audio CircuitA Complex Audio Circuit

Open CircuitsOpen Circuits

The Circuit is a Load on the The Circuit is a Load on the Voltage SourceVoltage Source

The circuit is where the energy of the The circuit is where the energy of the source (battery) is carried by means of the source (battery) is carried by means of the current through the the various current through the the various components.components.

The battery is the The battery is the sourcesource, since it , since it provides the potential energy to be used.provides the potential energy to be used.

The circuit components are the The circuit components are the load load resistanceresistance - they determines how much - they determines how much current the source will produce.current the source will produce.

Direction of Electron FlowDirection of Electron Flow The direction of electron flow in our circuit The direction of electron flow in our circuit

is from the negative side of the battery, is from the negative side of the battery, through the load resistance, back to the through the load resistance, back to the positive side of the battery.positive side of the battery.

Inside the battery, electrons move to the Inside the battery, electrons move to the negative terminal due to chemical action, negative terminal due to chemical action, maintaining the potential across the leads.maintaining the potential across the leads.

Electron Flow in a Simple Electron Flow in a Simple CircuitCircuit

DCDC Circuits that are powered by battery Circuits that are powered by battery

sources are termed sources are termed direct currentdirect current circuits.circuits.

This is because the battery maintains the This is because the battery maintains the same polarity of output voltage. The plus same polarity of output voltage. The plus and minus sides remain constant.and minus sides remain constant.

Waveform of DC VoltageWaveform of DC Voltage

Characteristics of DCCharacteristics of DC It is the flow of charges in just one It is the flow of charges in just one

direction and...direction and... The fixed polarity of the applied voltage The fixed polarity of the applied voltage

which are characteristics of DC circuitswhich are characteristics of DC circuits

ACAC An alternating voltage source periodically An alternating voltage source periodically

alternates or reverses in polarity.alternates or reverses in polarity. The resulting current, therefore, The resulting current, therefore,

periodically reverses in direction.periodically reverses in direction. The power outlet in your home is 60 cycle The power outlet in your home is 60 cycle

ac - meaning the voltage polarity and ac - meaning the voltage polarity and current direction go through 60 cycles of current direction go through 60 cycles of reversal per second.reversal per second.

All audio signals are AC also.All audio signals are AC also.

Waveform of AC VoltageWaveform of AC Voltage

Complex VoltageComplex Voltage

This is a more realistic view of what This is a more realistic view of what an audio signal’s voltage would look likean audio signal’s voltage would look like

Comparison of DC & ACComparison of DC & ACDC VoltageDC Voltage AC VoltageAC Voltage

Fixed polarityFixed polarity Reverses polarityReverses polarity

Can be steady or vary in Can be steady or vary in magnitudemagnitude

Varies in magnitude Varies in magnitude between reversals in between reversals in polaritypolarity

Steady value cannot be Steady value cannot be stepped up or down by a stepped up or down by a transformertransformer

Used for electrical power Used for electrical power distributiondistribution

Electrode voltage for tube Electrode voltage for tube and transistor ampsand transistor amps

I/O signal for tube and I/O signal for tube and transistor ampstransistor amps

Easier to measureEasier to measure Easier to amplifyEasier to amplify

Heating Effects the same for both AC and DC current

Many Circuits Include both Many Circuits Include both AC & DC VoltagesAC & DC Voltages

DC circuits are usually simpler than AC DC circuits are usually simpler than AC circuits.circuits.

However, the principles of DC circuits also However, the principles of DC circuits also apply to AC circuits.apply to AC circuits.

ImpedanceImpedance Impedance is resistance to current flow in Impedance is resistance to current flow in

AC circuits and its symbol is AC circuits and its symbol is .. Impedance is also measured in ohms.Impedance is also measured in ohms.

Grounding Grounding In the wiring of practical circuits one side of the voltage In the wiring of practical circuits one side of the voltage

source is usually grounded for safety.source is usually grounded for safety. For 120 V - ac power lines in homes this means one side For 120 V - ac power lines in homes this means one side

of the voltage source is connected to a metal cold water of the voltage source is connected to a metal cold water pipe.pipe.

For electronic equipment, the ground just indicates a For electronic equipment, the ground just indicates a metal chassis, which is used as a common return for metal chassis, which is used as a common return for connections to the source.connections to the source.

Common Symbols/ Names for Common Symbols/ Names for Ground in Electric CircuitsGround in Electric Circuits

Ohm’s LawOhm’s Law The amount of current in a circuit is The amount of current in a circuit is

dependent on its resistance and the dependent on its resistance and the applied voltage. Specifically I = E/Rapplied voltage. Specifically I = E/R

If you know any two of the factors E, I, and If you know any two of the factors E, I, and R you can calculate the third.R you can calculate the third.

Current I = E/RCurrent I = E/R Voltage E = IRVoltage E = IR Resistance R = E/IResistance R = E/I

Current is Directly Proportional to Current is Directly Proportional to Voltage for a Constant ResistanceVoltage for a Constant Resistance

OHM’s LAWOHM’s LAW

Current is Inversely Proportional to Current is Inversely Proportional to Resistance for a Constant VoltageResistance for a Constant Voltage

OHM’s LAWOHM’s LAW

PowerPower The unit of electrical power is the watt.The unit of electrical power is the watt. Power is how much work is done over time.Power is how much work is done over time. One watt of power is equal to the work done in One watt of power is equal to the work done in

one second by one volt moving one coulomb of one second by one volt moving one coulomb of charge. Since one coulomb a second is an charge. Since one coulomb a second is an ampere:ampere:

Power in watts = volts x amperesPower in watts = volts x amperes P = E x IP = E x I

3 Power Formulas3 Power Formulas P = E x IP = E x I P = IP = I2 x 2 x RR P = EP = E2 2 / R/ R

Conversion FactorsConversion FactorsPrefixPrefix SymbolSymbol Relation to Relation to

basic unitbasic unitExamplesExamples

MegaMega MM 1,000,000 1,000,000 or 1x10or 1x1066

5MΩ =5MΩ =5x105x106 6 ΩΩ

KiloKilo kk 1,000 or1,000 or1x101x1033

18kV =18kV =18x1018x1033 V V

MilliMilli mm .001 or .001 or 1x101x10-3-3

48 mA = 48 mA = 48x1048x10-3-3AA

MicroMicro .000001 or.000001 or1x101x10-6-6

1515V =V =15x1015x10-6-6VV